Lecture 5. Enzymes in Cellular Context and in Technological and Medical Applications Flashcards
Where do a few enzymes exist and in what form?
A few enzymes exist as single polypeptides free in cytoplasm or extracellular medium
What do most enzymes form?
Parts of larger organised structures
How many stages are there in the oxidation of sugars in mammals?
3
How are carbohydrates stored in mammals?
As particles of glycogen
Where are enzymes of glycogen synthesis and breakdown located?
Bound to glycogen particles
What happens in glycolysis and what is produced?
Glucose is converted into pyruvate which yields ATP and NADH
Where does glycolysis take place?
In the cytoplasm
Where does the citric acid/TCA cycle take place?
In the mitochondrial matrix
What are the products of the TCA cycle?
CO₂ and NADH
How is NADH re-oxidised?
By O₂ through a series of oxidation/reduction reactions (electron-transfer chain)
What is the ribosome?
A complex multi-component enzyme machine for making proteins
What is the proteasome?
A complex of two types of subunit to make a tightly-
controlled protein degradation machine in the cytoplasm and nucleus
What is a frequent feature of multi-enzyme complexes?
The different activities are located in sequential regions of the structure
How expensive will the enzyme market be by 2024?
$9.5 billion
What contributes the most amount of money to the enzyme market?
Cleaning
Traditionally, what does food bio-processing involve?
Intact microbes naturally present in food environment
What is rennet?
A mixture of enzymes from the stomach of unweaned calves
What is chymosin?
An aspartyl protease which digests casein, the major milk protein
What does the digestion of casein do?
It destablizes fat droplets so milk clots, separating ‘curds’ and ‘whey’; first step in making cheese
Process of producing chymosin on an industrial scale
Clone the gene encoding the enzyme and express it in bacteria or fungi
Grow the modified bacteria/fungi in biofermentors
Purify the protein
What are proteases used for in the meat, leather and textile industries?
Proteases can be used to treat animal hides to remove hair and to soften skin
Proteases can be used to ‘tenderise’ meat
What are cellulases used for in the meat, leather and textile industries?
Cellulases are used to treat denim to generate ‘stone-washed’ texture and look
Since the 1970s, how have high-fructose syrups been made?
By including bacterial glucose isomerase
What is used as the main sweetener in ‘diet’ drinks?
Aspartame/E951
How does the hydrolysis of peptide bonds caused by proteases reversed?
A low-water-content solvent system (mainly organic solvent) is used to reverse the normal equilibrium
What enzyme is not denatured in an organic solvent?
A thermo-stable protease named thermolysin
Why are immobilised enzymes important?
They are usually more stable and more readily recoverable from reactor
When does “beer haze” occur?
Often caused by barley and yeast proteins, especially at low temperatures
How is ‘beer haze’ treated?
‘Chill-proof’ with proteases e.g papain
What causes cloudiness in fruit juices?
Pectins from plant cell walls
How is cloudiness removed from fruit juices?
Treated with pectinases
What are enzymes better than chemistry for?
Stereo-specificity and positional specificity
What are prime examples of fine chemicals that
require positional and stereo-specific synthesis?
Pharmaceuticals
What is penicillin acylase used for?
Penicillin acylase is used to make semisynthetic penicillins
What are biosensors?
Biosensors are (electronic) analytical devices giving direct read-out. Most biosensors are based on enzymes
